The present invention relates to an apparatus for repairing joints, cracks, or leaking points in underground hollow pipe such as water pipe, sewer pipe, or cable duct.
Underground pipes can generally be classified into three categories: (1) large diameter pipes which allow free access by a man and repair equipment; (2) medium diameter pipes which allow a man to enter such as by crawling, but which are too small to allow easy handling of equipment and repair; and (3) small diameter pipes which a man cannot enter.
In repairing a small diameter pipe such as in category (3) above, it is possible to employ a process such as is disclosed in Japanese Pat. No. 929,664 (laid-open publication No. SHO 49-118210). In this process, an expandable bag is inserted into the pipe and is pneumatically inflated to bring the bag into firm contact with the inside wall of the pipe. Thereafter, a hardenable chemical (grout) is poured between the pipe and the bag through an aperture in the bag to seal the leak.
In repairing large diamater pipes as described above in category (1), a worker can manually place an annular rubber sheet into engagement with the pipe wall and the sheet can be pressed (expanded) into engagement with the pipe wall by manually operated jacks. Thereafter, the hardenable chemical (grout) is poured through an opening in the sheet to seal the pipe leak.
The difficulty has arisen with respect to repairing leaks in the medium size pipes described above in category (2). Thus, in that category pipe, it is dangerous to utilize the pneumatically expandable bag described above for category (3). The large amount of high pressure air required for inflating the bag in this environment stores up an enormous amount of potential energy which, if the bag breaks, can result in an explosive air flow. Also, difficulties arise in attempting to align the grout opening through the bag with the pipe leak location. The technique described above for the large diameter pipes, category (1), also is not particularly useful for the medium diameter pipes because of the confined area inside these pipes and the requirement that the jacks be manually actuated.